The compressor section of a Gas Turbine Engine (GTE) often includes multiple axial compressor stages positioned in succession. Each axial compressor stage typically contains a rotor disposed immediately upstream of a stator. The compressor rotors are essentially bladed wheels, which are surrounded by a tubular casing or shroud. Each compressor rotor may be mounted to a shaft of the GTE. During operation, the compressor rotors rotate along with the shaft to compress airflow received from the GTE's intake section. The final axial compressor stage discharges the hot, compressed air, which can be supplied directly to the engine's combustion section for mixture with fuel and subsequent ignition of the fuel-air mixture. Alternatively, the airflow discharged by the final axial compressor stage can be fed into a centrifugal or radial compressor stage, which further compresses and heats the airflow prior to delivery to the engine's combustion section.
As compressor pressure ratios improve, so too does overall GTE performance potential. Several different approaches have traditionally been employed to improve compressor pressure ratios. These traditional approaches include increasing the compressor stage count, increasing the aerodynamic loading of the compressor, and increasing the rotational speed range over which the compressor section operations. Each of the foregoing approaches is, however, associated with a corresponding tradeoff or penalty. For example, increasing the number of compressor stages adds undesired length, weight, and cost to the GTE. Additionally, increasing the number of compressor stages can degrade performance matching for off-design GTE operation. Increasing the aerodynamic loading of the compressor often negatively impacts compressor stall margin. Finally, increasing the rotational speed range over which the GTE operates typically reduces compressor efficiency and can shorten the operational lifespan of the engine components.